The present invention relates to a remote control apparatus, particularly a pneumatic remote control apparatus, for operating and controlling a machine such as a crane from a variable location spaced from the machine.
It is often necessary for an operator when operating a crane from its cab or from a control box secured to the cab or a truck on which the crane is mounted to be directed by a person having a better view of the work area in which the crane is operating and of the load being lifted and/or moved by the crane. Remote control apparatus are known for operating various crane functions such as movement of the hoist, trolley, boom and swing. However, such remote control apparatus suffered from the disadvantage that it was connected to the crane by electrically conductive structure so as to expose the crane operator to the hazards of electrical shock should the crane strike electrical wires or other sources of current. U.S. Pat. No. 4,307,810, issued Dec. 29, 1981, discloses as a solution to this problem a remote control apparatus including pneumatic switches which is coupled to the crane by plastic tubing so as to electrically insulate the pneumatic switches from the crane, thereby avoiding the disposition of a highly conductive electrical path between the crane and the pneumatic switches.
The remote control apparatus in the '810 patent has the drawback however that a relatively long assemblage of tubing for carrying pressurized air between the pneumatic switches and the crane typically lies along the ground at the work site where it is subject to pinching and crimping. Such pinching and/or crimping can under certain circumstances result in a loss of control over the various crane functions from the remote control apparatus, thereby causing an unpredictable and possibly uncontrollable operation of the crane.
The invention disclosed herein eliminates the aforementioned drawback and enables all crane functions to be shut down automatically should a loss of control occur while operating the crane from the remote control apparatus.